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Vehicle owners always play down on the need for a detailed diagnosis and the importance of diagnostic results in fixing their vehicles. Some even claim that the scan tool was used and could not detect any fault in their broken down vehicle. The scan tool is only as functional as the diagnostic function understood by the technician, diagnostician or mechanic using such Scanner. Knowledge of the various scanner modes (Mode $01 to Mode $10) can never be over emphasized.

Some snap shots from one of my scanners.


With the exception of Code Readers, diagnostic scan tools are used for extracting fault codes (Pending, Current, Confirmed, Permanent), erasing codes, viewing live data, check vehicle monitors, biadirectional control of components, adaptations (program) e.t.c. The effective use of all scan tools is determined by the level of knowledge we have of these tools, it gives us the ability to play around its features and helps us to give better interpretation of the fault codes. We will be looking at the definitions and use of the different modes in our scan tools.

Mode $01: This feature is available on all generic scan tools of different brands. It gives the diagnostician the list, numbers, and value of the various sensors available on the vehicle, they are always regarded as PID (Parametric Identification). This PIDs are the calculated value of the various sensors by the individual system monitor and the ECU. 
A good example is the calculated engine load, this is generated by the ECU after comparing the Throttle Position Value, MAF reading and MAP reading. 

The PIDs are calculated from the current operational values or live data as the vehicle is operating. Some scanners can even go further to plot reading on a graph; this makes it easy to see the sensor response performance, a good way to know a bad MAF sensor, oxygen or A/F sensor, fuel trim analysis e.t.c. 

The mode $01 also helps us know which monitors ran a test and what their result it. The monitor is simply an examiner, it alters some value in the vehicle system and uses the result from the monitored sensor to know if the sensors are good or bad. Hence a monitor would either PASS, FAIL or is in an INCOMPLETE state. 

PASS: Monitor ran a test as at when due and all sensors and system components are responding,

FAIL: Monitor ran a test over and over again and discovered that a sensor or components are not responding .

INCOMPLETE: For the On Board Diagnostic (OBD) to be free from clash of importance, various monitors are meant to run only when some Vehicle operational values are attained and only when some other tests are ‘PASS’. INCOMPLETE means the operational value i.e required Coolant Temperature has not been attained and their status are still unknown.

Mode $02(Freeze Frame Data): Access to Freeze Frame Data is important when diagnosing vehicle fault. It’s simply defined as the various calculated PIDS or Sensor Values that were available on the vehicle as at the point when the MIL (Malfunction Indicator Lamp or ‘Check Engine’ light) was turned ON by a registered Fault Codes. Bear in mind that only faults and consequently fault codes that affect the emission system will turn on the MIL. 
However, some manufacturers have designed the MIL to turn on when some other drivability faults that will affect vehicle performance are detected. Some things to note about a freeze frame data are: Never clear any Codes without recording the freeze frame; if you do, you would have lost your lawyer in a court hearing. Take note of values, such as, Engine RPM, Engine Load, MAF and MAP values, ECT (engine coolant temperature sensor) Fuel Trims (Short Term and Long Term), Oxygen sensor or A/F sensor values, VSS (Vehicle Speed sensor), e.t.c.; if possible record them all. These data will be useful in simulating the fault again and to confirm if the fault was fixed. 

Mode $03 (View stored codes): This feature gives the diagnostician a quick interpretation of the various fault codes in the OBD II fault memory. Unlike Code Readers that will display only the Alphanumeric Code. Mode $03 displays the meaning/definition of the codes. Most times due to the lengthy list of codes, we may need to scroll down to view more pages. Bear in mind that some scan tools will display the list of Fault Codes by Vehicle System and most scanners will give you an option of reading codes from ALL SYSTEMS or SPECIFIC SYSTEM. While viewing all system Codes the system that registered the fault will be displayed beside each Codes. Another cool function on some scanner are the display of PENDING CODES, CURRENT CODES, PERMANENT CODES, TEMPORARY CODES & HISTORY.

Mode $04(Clear Trouble Codes): This feature is essential for all generic scan tools, be it the base model, Elite or Pro. It enables the scan tool to Read and Erase fault Codes. But we need to bear in mind that using mode $04 will clear and reset the OBD memory and even ECU in some vehicle brand. This means we should always record the Fault Codes and Freeze Frame Data before you initialize this mode. Mode $04 will be shown as a function READ CODES and CLEAR CODES on the scan tool. The READ CODE functions on some scanners will be multiple depending on the number of systems in the vehicle i.e. We can read code from PGM-FI, ABS, Anti-theft and Immobilizer, Controller Area Network (CAN) e.t.c. 


Mode $05(Oxygen Sensor Monitoring): This feature gives the display of the heated oxygen sensor or simply put as Oxygen Sensor monitor screen and its calculated value. This may be displayed in graphical form of numerical value, but most diagnosticians and automobile technicians will agree that the former is more useful in diagnosis of oxygen sensor, this is because the oxygen sensor (Lambda sensor) will always oscillate between LEAN and RICH when functional. Data pertaining to mode $05 can be viewed as Live Data and as Oxygen Sensor Monitor Status. When viewing the Live Data, you are reading the instantaneous value that the vehicle is operating with at either KOER (Key ON, Engine RUNNING) or KOEO (Key ON, Engine OFF). This value will vary as the engine load or RPM is altered, that’s why it is better viewed as graphical format; with this view we can detect if the Oxygen Sensor is functional, dead or failing intermittently. The oxygen sensor values are always given in Volts or millivolts and bear in mind that a threshold value of 0.1V to 0.44V represents a LEAN condition, while a threshold value of 0.46V to 0.9V is regarded as a RICH condition. 

With the introduction of A/F (Air/Fuel) Ratio sensors many diagnosticians have gotten confused, this is simply because the A/F ratio sensor will display its value in Amperes and it does not oscillate like the Oxygen Sensor. The remaining is intricate, just keep reading.

Mode $06(Test Information for Non-Continuous Monitors):
This feature is used to access the raw (TIDs & CIDs) script of the various Non Continuous Monitors in the Vehicle even before their results are out. To better understand this; imagine how a teacher knows a student will fail or pass at the end of the term, he knows by checking their various assessment scores, assignment scripts and exam scripts. This is just the same way the Mode $06 operates. However this gets more complex on a scan tool as the ‘scripts’ are shown in Hexadecimal Numbers (Base 16, not in Base 10). But it certainly proves very useful when diagnosing intermittent faults. However, we need to bear in mind that Mode $06 data will always look different in various vehicles and scan tools.

Mode $07(Test Information for Continuous Monitors): This feature is similar to Mode $06 except that it functions for Continuous Monitors only. The various continuous Monitors in a vehicle are the Misfire Monitors, Fuel System Monitors, Oxygen Sensor Monitors (certainly A/F Ratio Monitors too) and Comprehensive Component Monitors. With the Mode $07 a misfire count can be read while diagnosing the vehicle, an injector pulse-width can be read and a lot more. This means that before a vehicle misfire reaches a level where it will be registered as a Code, say above 30 Misfires per 200 Revolutions, you can use the Mode $07 Misfire Monitor results to know the misfire status and recommend a repair for that client. There are lot more to this but the previous example is just perfect to describe the Mode $07 operations. 

Mode $08(Bi-Directional Communication): This feature gives us the ability to power electrical components in the vehicle with the aid of a scanner. It is called Bi-directional Control of Components. We simply operate the component while at the driver’s seat; nothing stressful, just click a button and various component will operate. This feature is available on Enhanced Generic Scanners and Manufacturer Specific Scan Tool. This function will be appreciated when the need arises to test the functionality of an electrically powered component, simply Bi-directionally control the component and we observe for operational clicking sounds or signs on the vehicle performance. In most scanners you find this function under specialized diagnostic function. 

Mode $09(Display Vehicle Information): This is used to access vehicle details, ECU software details, VIN details, Engine Size e.t.c. We might consider this not useful until we are to diagnose a vehicle whose VIN tag has been removed and its model tag removed. A diagnostician will simply hook up his diagnostic tool and read all this details from the Mode $09 diagnostic tool function.

Mode $10(Permanent Emission Codes): The tenth mode of diagnostic scan tools is a rather recent invention. This mode gives emissions-related trouble codes, and essentially serves at a shield against tinkerers trying to circumvent emission laws. The purpose of mode $0A, referred to as Mode 10, is to allow a scan tool to obtain DTCs that are stored as “permanent codes.” These are codes only the module can clear. Even if you’ve made a successful repair and have cleared the codes in Mode $04, these codes will remain in memory until the computer has completed its own system test. 
The mode was put into place in 2010, with full usage by 2012. The goal was to counter individuals who shut off the check engine light before an emissions check. Prior to 2010, disabling the light would result in no error codes, even if the vehicle had an issue. This essentially gave the vehicle a free pass during an emissions inspection.
With Mode 10, however, codes that fall under the mode’s jurisdiction will only clear when they monitor a full cycle, which it can’t do if the light is disabled. Codes that fall under Mode 10 are often called “permanent codes”, because they are stored in the computer for a long timeframe, making them, (as far as emissions tests are concerned) permanent.

Be a fixer not a part fitter…. Stay Dirty!


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